Space charge measurements in ionomer films exposed by corona discharge

Ionomers are thermoplastic polymers functionalized by metal ionic groups attached to backbone chains of the host polymers. The ion groups form clusters and crosslink the backbone chains. In contrast to the ordinary covalent bond structure, for crosslinkage with ions, the bond energy decreases at high temperature. Ionomers, therefore, retain thermoplastic properties, although the function of the ionic clusters has not been theoretically explained. The adhesion strength and miscibility of host polymers are also improved by the ionic radicals. Among many kinds of host polymers, ethylene methacrylic acid copolymer is the most common base resin for manufacturing ethylene ionomers. Ethylene ionomers are used in skin packaging technology, such as polymer laminated papers and aluminum coated polymer films. It has been recently found that an ethylene ionomer can store charges after corona discharge exposure from surface potential measurements. As a part of plasma chemistry, the effect of corona discharge on polymers is usually restricted to analysing surface properties. The pulsed electroacoustic (PEA) method was used to measure space charge distributions through the thickness of ethylene ionomer specimens which include Mg or Al ions